/Engine/Source/Runtime/SlateCore/Public/Input/Reply.h
An event should returnFReply::Handled().SetUserFocus( SomeWidget ) as a means of asking the system to set users focus to the provided widget
[FReply](API\Runtime\SlateCore\Input\FReply) & SetUserFocus ( [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > GiveMeFocus, EFocusCause ReasonFocusIsChanging, bool bInAllUsers )